Tool for Solar Thermal System Schematic

I've started down the road of putting together a drainback system for my house in sunny San Francisco. If you're curious what I'm up to, I'm documenting the process here: http://sfsolarhotwater.blogspot.com/

I'm at the point that I'd like to create some system schematics. I *love* the design of the schematics published in Homepower magazine, but I've struck out trying to find the tool HP uses or anything like it. What are you all using? I need to get this ugly, `key free' SRCC OG-300 diagram: